The present invention relates to a matrix for a catalytic reactor for the purification of exhaust gas, particularly for internal-combustion engines, that has either a corrugated or a smooth and a corrugated metal strip that are wound or folded into several layers that are adjacent to one another and are at least partially soldered to one another.
The production of a matrix for a catalytic exhaust gas reactor by winding a smooth and a corrugated metal strip into several layers on top of one another is shown in German Published Unexamined Patent Application No. 2,924,592. In that matrix, between the layers that are wound on top of one another, by means of an application arrangement equipped with rollers, soldering material in strip form and also continuously is applied to the smooth strip or in each case on the extreme elevations of the corrugated strip. The soldering material is then melted in a furnace. It is also known from this text to, instead of soldering material, include soldering strips in the individual windings.
This last-mentioned method has the advantage that this soldering strip, in a relatively easy way, can be wound into the matrix and held by the layers that are located on top of one another, until the matrix is soldered in the furnace. However, it is a disadvantage that the matrix, because of the winding-in-between of soldering strip, even if it has only a small thickness of fractions of a millimeter, increases its diameter as a result of the winding of several layers on top of one another. Further, during the soldering process in which the wound-in solder melts, a settling takes place that may result in an uncontrolled change of the diameter of the matrix that can then no longer, or at least not in the required manner, be pressed into a shell.
As a rule, a soldering-together of the individual layers over the whole axial length of the matrix did no take place, and only the front sides of the wound matrix was dipped into a soldering bath so that the matrix in each case was soldered together only at the front sides. It was found that this soldering-together at the front sides is not sufficient in all cases.
The objective of the present invention is to provide a matrix for a catalytic reactor for the purification of exhaust gas which will not change diameter during the winding process, the folding process, nor during a subsequent soldering process.
This and other objectives ar achieved in the present invention by providing a matrix which has at the areas of the corrugated strip that border on the adjacent layers, small radial indentations in which the material that is used for the soldering is received.
This above arrangement makes possible in a simple manner to also wind in the soldering material, for example, soldering strips, in a known manner during the manufacturing. In the present invention, however, the wound or folded strips rest directly against one another, and the soldering material is present only in the intermediate areas in which the indentations are located without increasing the diameter of the matrix. The soldering material will then ensure the firm connection of the layers located on top of one another. In certain preferred embodiments of the present invention, the indentations are arranged in radial planes, in which the soldering strip or the soldering material is introduced in parallel to the feeding direction of the strips to be wound. In other preferred embodiments, the indentations extend spirally on the generating lines of the wound layers, so that a corresponding feeding of the soldering strip or the soldering material must be provided. This is relatively easy to implement.
The indentations, in a very simple manner, are created in a preferred process, for example, by a sufficiently firm soldering wire that is under a corresponding tensile stress which is wound into the matrix at the outer areas of the corrugations. As a result of the radial force caused by its tensile stress, the soldering wire presses itself into the relatively soft material of the corrugated strips, at least to such an extent that it does not protrude over the extreme areas of the corrugations. However, it is also contemplated to provide during the production of the corrugations of the metal strip that the corresponding indentations are pressed into the extreme areas of the corrugations. This may take place, for example, by a pair of indenters that, at its circumference, has surrounding ribs of small dimensions that press in the desired indentations either in the radial plane or in spiral form.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.